Electron ray indicating device



Feb. 12, 194e. J, A, HULTQUIST 2,394,857

ELECTRON RAY INDICATING DEVICE Original Filed July 23, 1940 ATTORNEY Patented Feb. 12, i946 ELECTRUN RAY ENDICATKNG DEVICE l?. Albert Hultquist, Scarsdale, N. Y., assigner to Radio Corporation of America, a corporation of Delaware (Cl. Z50-27.5)

4 Claims.

This invention relates to electron ray indicator tubes and is a division of my copending application, Serial #345,918, led July 23, 1940.

In frequency modulation receivers it is eX- tremely important that the receiver be tuned to the exact center of deviation of the transmitted wave in order to avoid distortion and noise. Previously known systems, of which I am aware, for indicating correct tuning of frequency modulation receivers depend on the use of a meter or electron ray tube so connected as to give an indication proportional to the voltage developed on the grid of the limiter stage in the receiver, avery sensitive zero center voltmeter across the output of the discriminator stage, or a dual shadowY electron ray tube with one of its associated amplifiers connected to one end o-f the discriminator" output circuit and the other connected as a phase inverter. Correct tuning in the first mentioned system is indicated by a maximumgrid potential or a closure of the shadow of the electron ray tube. However, this system is rather insensitive to variations in tuning since the response characteristic of the tuned circuits in the receiver is quite broad. It is, therefore, difficult to adjust the receiver for equal response to equal frequency deviations on each side of the midfrequency. Furthermore, the maximum response at this point in the receiver has no relation to the tuning of the discriminator stage and ifany change in tuning takes place there the tuning indicator can no longer be relied upon.

VZin theI last of the above mentioned systems proper tuning is indicated by equal sized shadow areas on both sides of the tube. The comparison of a two shadow area is attended with some difficulty since the broadest parts of the shadows are separated by a considerable distance.

The use of a Zero center Voltmetcr overcomes the foregoing disadvantages but it is expensive and easily damaged.

-An object, therefore, of the present invention is to overcome the above mentioned difficulties.

A further object of the present invention is the provision of a simple, inexpensive system for indicating correct tuning of a frequency modulation receiver, l

Another object of the present invention is the provision of an electron ray structure for giving an indication of the relative intensities of a pair ofpotentials in the form of substantially triangular shadow/ areas with variable length bases, said bases' being closely adjacent for ready comparison;

" Still a further object is the comparison of the relative magnitudes of a pair of independent potentials.

The foregoing objects, and others which may hereafter appear, are attained by providing a novel form of electron ray indicator tube having a luminous coating 0n an anode in the form of a pair of intersecting plane surfaces between a pair of separate emitting cathodes and shadow control electrodes. The line of intersection of the planes is in a plane perpendicular to a line between said cathodes. Electron beams `from each of the cathodes impinging on the adjacent surface of the anode cause the luminous material thereon to fluoresce. The control electrodes cast triangular shadows on the anode, the width of the shadow at the apex of the anode being proportional to the Voltage applied to the ray control electrodes. Since the widest parts of the shadows are closely adjacent they may be readily compared.

The present invention may also be embodied in a pair of conventional single shadow electron ray tubes with their areas placed as closely adjacent as possible, or a tube of the type disclosed in a prior Roberts Patent #2,175,700, granted October l0, 1939, may be utilized, interposing between the end of the tube and the eye of the observer a pair of reversing prisms so that the widest parts of the shadows appear adjacent to each other.

The present invention will be more fully understood by reference to the following detailed description, which is accompanied by a drawing in which Figure 1 is a circuit diagram illustrating the application of my invention to the discriminator circuit of a frequency modulation receiver; Figure 2 is an end View of an embodiment of the present invention and illustrates the indication given when employed in a circuit as shown in Figure 1; Figure 3 is a View partly in section of the embodiment of Figure 2, while Figure 4 illustrates a modication of the invention.

In Figure 1, I indicates generally a discriminator transformer of the frequency modulation receiver. Frequency modulated signals of a constant amplitude are applied to the primary II. To the secondary I2 of the transformer are connected the anodes of rectifier tube I4. The windings of the transformer are tuned to the desired frequency by means of adjustable condensers I3, i3. Across the cathodes of rectifier I4 is connected an output circuit comprising resistors I5, l5 shunted by'radio frequency bypass condensers Il, I8.'V One end of the output circuit is grounded and the other end is connected to an audio frevention and the theory of its operation will notl here be gone into. However, itis important lto understand that when the circuit is properly tuned to a signal to be receivedjthepotential across resistor I is equal inmagnitudeand-op.

posite in polarity to that across resistor I6. Therefore, no D. C. potential dierence exists between lead and ground. On one side ,of resonance 23 will become positive due to anfincrease in potential across resistor I5 and a decrease across resistor IG, while on the otherside oi?v resonance the reverse .condition will .beetrue The theory of operation of the discriminator. cire.

cui,t ism ore completely discussedk inta-*Seeley Patent #2,121,103, .granted- June-2l,V 19,38, and

ref erenceinay be made to thatv patent for a iur ther disclosure.`

Through a decouplingcircuit 25,.-.2614 agridZ'I ofV anamplifier; and' phase inverted tube is connected to the upper end ofv load circuit I5.. I6.

The time-constant of circuit 25, 2l;y shouldbe high enough that, the-.audio frequency signalis-.filftered out and doesnot appear on grid 2l.,V Dual triodeampliiier tube 28, may, ofcourse, be..=re

placedby a` pair yof .physicallyseparate triodesJv if .'desired. Anodes 29 .and3Il--of the amplifier tubrewv28.- are connectedl to the positive sides rotta, v

source-v of.. anode potential indicated as; B+. through resistors 3I and32.k Thefothensidednf the anode potential source is grounded. The cathodes are connected together and to ground. through resistor 39.`

Indicatortube 33 has rayvcontrol electrodes. 34 and 35 connectedto anodes-sZS andz, respeca tively.V The `anode l 36 of; indicatory tube 33 andl its eathodes 311,; 38,. are@ connected'- te, the anode supply source- .inrthe .eQnyeriiier.1elv mamler-v The magnitudes of. plate resistors 31;. 32@andthe.corri-y rnonfcatliode lresistor; ,39, associated with tube v2 8 arreso-adjusted; that with no Vpotential onggrid 21, equal potentials, somewhat lower thanlthe potentiellen, anode or; target.- 35, are impressed on ray. control. electrodes. Y34,135. Ofinclicator tube-...33. The f. shadows Cast 0n. the luminous surfaces-oi enodei therefore. of,- equelsize. asshownin Figurez, When grid21 has a poStVepotential applied thereto.. the. plate current threliehf,refV sister- 3 IA increases causnefeentrolencender-34ste become more negative thus4 increasing the vwiel/th of the shadow; castv thereby on. luminnisV surface of; anodel. The increased currentfflow; through resistor 'rcauses the grid. 2,1 of. ft11e,:phaseinev verter tube 28 to become leffectiveliimore negen tive with respectggto an,odejll,A decreasing KV,the anodecurrentthrough yresistory32., Thepotentialon ray controlelectrode 35 ofr indicator tube 33.- thereiore :becomes more positive..` decreasing the .Width of; its .shadow mrthe -1umine11.s; surface ofanode 3B., The reverseactiontakesplace when grid21 has a negative potential appliedthereto.

It will be notedthat a pair oftriangularshadows are vformed having closely adjacent variable length bases. It will` be readily. seen thatit is very easy to Adetermine by inspection the; relative sizes of thebases of the two` triangles). perfect resonance being indicatedby the shadowedges cast by the two ray control electrodes 34, 35 being exactly adj-acent.

When the receiver is tuned to a frequency remote from any incoming signal the same indication is obtained. As the tuning of the receiver is varied and resonance with a received signal is approached. the lengthxoi thefbase op one of the shaded'areas increases and that of' the other decreases until a certain ratio, dependent upon the constants of the circuits and the strength of the-signal,.is attained. Then as resonance is still more closely approached the larger shaded area decreases in size and the smaller one increases until'thebase lengths are again equal. The receiver is 'thencorrectly tuned. Upon a contintion. The 4form` of. the, bil-pianar anodeor-target 36 is clearly show-n inthis iigure.- Ray rcontrol electrodes 34 and 35 yand cathodes 31 and .38farex constructed yin` the same f manner 'as .described in the heretofore mentioned-Roberts` patent. rLike,y wiseshieldingcaps 40 and 4I are provided Vover,

the ends of the cathode and rayl controlaelec trodes inA order to shield the .eyeA of the'observerz from the direct light .offthecathodes.andimorder` toprevent fluorescence of the.glass:enveloppenn If desired, semiecylindrical shells.. supporting caps 40 .and4 4I may be substitutecl.forV

ofthe tube.

supporting rods 43 in; order f tofrprevent -luores--v cenceon-the sides of the-glass envelope-142.2, Fur#` therrnore, insome casesfit, may -be-desirableto.

provide arl-ow wall/ bisectingj the. externalA sangle.. between the planesI `of4 anode 3 6 Afor; this esame purpose, and to preventv a. spill-over?? Vof .-iiuore" esoerice at` the.A apex oftheanode. Thefwall, be-A ingl thin, andA in aplane parallel ,totthefline-of sight. of `the observer r,causes-nowobstructionatof visions Grids 31 andy38( mayfsurround.cath?,4

odes. 3l .and 38: for limiting the space-current. drawn from the cathodeseii,desir-ed..v The rele:

ments. withiny the glass envelopeAZ .are supportedv in` position lay-support rodsA 5A and Vmica-discsffA-G..v

as is customary f practice ine the .,construction` ofI thermionic discharge tubes.

A moolication of. thepresent'v invention is; shown, inv Figure -,4- wherein; an electron rayetubev of the typeV showndnl the vRoberts.--.-Pate nt #2,175,700 isused in thefcircuit; shown -in Figure 1. Thetube is indicated generallyffbygreference character-5'ILV Inorder to causetheabroadest parts of: theshadow areas. tolappear, fadjacentpa.v

ditionA of jthe` indicatingussystem. mayl Ibeliad by:

tuning the.. receiver awayv from ,fanyssignal 01111034 removing the rectifier tube I4. The absence oaV wenn.'

diamondshaped shadowarea `as .shownen meure 2 indicates that the balance of the indicating circuit has become disturbed through variation of the circuit elements or aging of the tubes. Resistors 3| and 32 must be varied to again arrive at a balance or amplifier tube 28 and/or indicator tube 33 replaced.

I claim:

l. A thermionic discharge tube having an anode in the form of a pair of intersecting planes, said anode having a luminescent material thereon; a pair of cathodes, one adjacent each anode plane, for directing a stream of electrons on dliferent surfaces of said anode whereby said areas become luminous, the line of intersection of the planes of said anode being normal to a line connecting said cathodes, ray control electrodes adapted to cast triangular shadows on the luminous areas of said anode, one ray control electrode being located between each of said cathodes and said anode and operative to control the length of the base of the triangular shadow cast thereby in proportion to potentials applied to said ray control electrode.

2. A thermionic discharge tube having an anode in the form of a pair of intersecting plane surfaces, said anode having a luminescent material thereon, a pair of cathodes adjacent said f control electrodes.

3. A thermionic discharge tube having an anode in the form of a pair of intersecting plane surfaces, said anode having a luminescent material thereon, a pair of cathodes one on each side of the intersection of said plane surfaces, an

imaginaryrline connecting said cathodes/inter- Y seating said plane surfaces, and ray control electrodes positioned along said imaginary line and located between said cathodes.

4. A thermionic discharge tube having a dihedral anode, said anode having a luminescent surface, a pair of electron sources one on each side of an intersection of the planes of said dihedral anode, and a ray control electrode positioned between each electron source and said anode.

J. ALBERT HULTQUIST. 

